In modern surgery, powered surgical tools are some of the most important instruments medical personnel have available to them for performing certain surgical procedures. Many surgical tools take the form of some type of motorized handpiece to which a cutting accessory like a drill bit, a bur or a saw blade are attached. These tools are used to selectively remove small sections of hard or soft tissue or to separate sections of tissue. The ability to use powered surgical tools on a patient has lessened the physical strain of physicians and other personnel when performing surgical procedures on a patient. Moreover, most surgical procedures can be performed more quickly and more accurately with powered surgical tools than with the manual equivalents that preceded them.
A typical powered surgical tool system, in addition to the handpiece, includes a control console and a cable that connects the handpiece to the console. The control console contains the electronic circuitry that converts the available line voltage into energization voltage suitable for powering the motor integral with the handpiece. Typically, the control console is connected to receive a signal from the hand or foot switch used to control the tool; based on that signal, the console sends appropriate energization signals to the handpiece so as to cause it to operate at the desired speed.
As the use of powered surgical tools has expanded, so has the development of different kinds of powered surgical tools that perform different surgical tasks. For example, a femoral reamer, used in hip replacement surgery is a relatively slow speed drill that operates at approximately 100 RPM, yet it draws a relatively high amount of power, approximately 400 Watts. Neurosurgery requires the use of a craniotome which is a very high powered drill that operates at approximately 75,000 RPM and that requires a medium amount of power, approximately 150 Watts. In ear, nose and throat surgery, micro drills are often employed. A typical micro drill rotates between approximately 10,000 and 40,000 RPM and requires only a relatively small amount of power, approximately 40 Watts.
As the number of different types of powered surgical tools have expanded, it has become necessary to provide each type of handpiece a mechanism for ensuring that it receives the appropriate energization signals. The conventional solution to this problem has been to provide each handpiece with its own power console. As can readily be understood, this solution is expensive in that it requires hospitals and other surgical facilities to keep a number of different consoles available, in the event a specific set of tools are required to perform a given surgical procedure. Moreover, in the event a number of different surgical tools are required in order to perform a given surgical procedure, it is necessary to provide the operating suite with the individual consoles required by the different handpieces. Having to provide these different consoles contributes to clutter in the operating suite.
An attempt to resolve this issue has been to design consoles that supply power to different handpieces. While these consoles have performed satisfactorily, they are not without their own disadvantages. Many of these consoles are arranged so that the medical personnel have to manually preset their internal electronics in order to ensure that they be provided the desired energization signals to the tools to which they are connected. Moreover, given the inevitable human error factor, time also needs to be spent to ensure that once configured for a new tool, a console is, in fact, properly configured. Requiring medical personnel to perform these tasks takes away from the time the personnel could be attending to the needs of the patient.
The Applicant's Assignee's U.S. Pat. No. 6,017,354, INTEGRATED SYSTEM FOR POWERED SURGICAL TOOLS, issued Jan. 25, 2000 the contents of which is explicitly incorporated herein by reference, appreciably eliminates the need to bring different control consoles into an operating room when surgical handpieces having different power requirements are used. In the disclosed system, each handpiece contains a NOVRAM. The NOVRAM stores data identifying the electrical power needs of the energy-producing component in the handpiece. The system also includes control console includes a processor and an energization circuit that for supplying energization signals applied to the handpiece. The types of the energization signals the energization circuit supplies to the handpiece vary as a function of command signals sent by the processor. Upon the connection of a handpiece to the control console, the data in the handpiece NOVRAM are read. These data are then used by the processor to regulate the output of energization signals by the energization circuit so that the appropriate energization signals are supplied to the handpiece.
Still another feature of the prior art system is that it is possible to simultaneously connect plural handpieces to the control console. The processor simultaneously stores the energization signal-describing data for each connected handpiece.
Thus, the prior art system, for many surgical procedures, essentially eliminated the need to provide an operating room with plural control consoles just because the handpieces being used had different power requirements. Moreover, the above system was further designed so that the console could be used to sequentially energize different handpieces without first having to remove the first and handpiece and then install the second handpiece.
Clearly, the prior art system provided a number of different cost and time efficiencies to the operating room. However, this system can, at a given instant, only supply power to a single handpiece. There are instances wherein for efficiency or necessity it is desirable to simultaneously actuate plural handpieces during a surgical procedure. For example, sometimes one surgeon will be harvesting tissue from one portion of a patient while a second surgeon is preparing another portion of the patient's body for insertion of the tissue. The present system is not able to simultaneously power the two separate surgical handpieces used to perform these separate procedures. If, in the interest of efficiency, there is an interest in performing these procedures simultaneously, two separate control consoles must be provided.
Moreover, many surgeons use footswitches to control their surgical handpieces and accessory instruments, for example, irrigation and suction pumps. It is a common practice to provide, on a single footswitch assembly, a number of different footswitches for controlling a number of different functions. For example, a single footswitch assembly may have individual footswitches for controlling the on/off state of the handpiece motor, the speed of the handpiece motor, the forward/reverse/oscillate direction of the handpiece motor and whether or not irrigation fluid is to be supplied.
Another limitation associated with known systems for driving motorized surgical handpieces concerns their ability to control the associated handpieces when the motors are operating at low RPMs. This problem is especially prevalent in systems employed to drive handpieces that include brushless, sensorless DC motors. The known systems operate by monitoring the back electromotive force voltage (BEMF signal) produced at the unenergized winding of the motor. A limitation associated with this control technique is that, when the motor is operating at a low RPM, the BEMF signal is often so low that it is difficult, if not impossible, to measure. Once this signal is undetectable, it can be no longer user to regular the commutation of the windings. Instead, brut force means are often used when the motor is started up in order to initially actuate the rotor. Also, this typical means that once a motor stalls as result of the motor reaching limit as the amount of torque that it can develop, the surgeon must totally deactivate, turn off, the motor before, the complementary control console can again apply a commutation signal to the windings. This results in the undesirable slowing of the surgical procedure.